<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
<script>
    ///集合取交集
    Array.intersect = function () {
        var result = new Array();
        var obj = {};
        for (var i = 0; i < arguments.length; i++) {
            for (var j = 0; j < arguments[i].length; j++) {
                var str = arguments[i][j];
                if (!obj[str]) {
                    obj[str] = 1;
                }
                else {
                    obj[str]++;
                    if (obj[str] == arguments.length)
                    {
                        result.push(str);
                    }
                }//end else
            }//end for j
        }//end for i
        return result;
    }

    //集合去掉重复
    Array.prototype.uniquelize = function () {
        var tmp = {},
            ret = [];
        for (var i = 0, j = this.length; i < j; i++) {
            if (!tmp[this[i]]) {
                tmp[this[i]] = 1;
                ret.push(this[i]);
            }
        }

        return ret;
    }
    //并集
    Array.union = function () {
        var arr = new Array();
        var obj = {};
        for (var i = 0; i < arguments.length; i++) {
            for (var j = 0; j < arguments[i].length; j++)
            {
                var str=arguments[i][j];
                if (!obj[str])
                {
                    obj[str] = 1;
                    arr.push(str);
                }
            }//end for j
        }//end for i
        return arr;
    }

    //2个集合的差集 在arr不存在
    Array.prototype.minus = function (arr) {
        var result = new Array();
        var obj = {};
        for (var i = 0; i < arr.length; i++) {
            obj[arr[i]] = 1;
        }
        for (var j = 0; j < this.length; j++) {
            if (!obj[this[j]])
            {
                obj[this[j]] = 1;
                result.push(this[j]);
            }
        }
        return result;
    };

    console.log(Array.intersect(["1", "2", "3"], ["2", "3", "4", "5", "6"]));//[2,3]
    console.log([1, 2, 3, 2, 3, 4, 5, 6].uniquelize());//[1,2,3,4,5,6]
    console.log(Array.union(["1", "2", "3"], ["2", "3", "4", "5", "6"], ["5", "6", "7", "8", "9"]))
    console.log(["2", "3", "4", "5", "6"].minus(["1", "2", "3"]));
</script>
</body>
</html>